Why Has No One Else Used the AR DI System?

[mjsdwash]

with all that super duper fantastic futuristic space age machined aluminum it still w

a loaded m16 a1 with a thirty round magazine and a 20' barrel weighs in at 7Lb. an ak 74 weighs about 9 1/2 with a 16 barrel doesent it? the difference is the entire weight of a 1911 and a spare magazine. I know we use the a2 now, but its still lighter, and were arguing about the base design. It was originally a 7lb 7.62x51, and i believe no one ever came close to that weight.



looks like im looking at the akm weight, not the 74. wikipedia says 7lbs unloaded. Now the 74 looks like a fun rifle

 

[Mosin Bubba]

Thanks for the great explanations and walk-thrus of the design, everybody. I've really learned a lot here.

I guess more generally, I don't know why DI never caught on. I know that a piston only adds one part and a few ounces to a gun, on the other hand designs like the MAS or AR save you that piston, and both seem to work pretty well.

Desert Eagle copied the AR Bolt design and barrel chamber for their pistols.

Really? I knew the Desert Eagle was gas operated, but I didn't know what kind of action it used.

Methinks you forget how light the original guns were; just 5-1/2 lbs with 20" barrels.

The original 5.56 rifles were that light? I knew they were under seven pounds, and that's already excellent for a full length rifle, but five and a half is just ridiculous.

Almost makes me want to build one.

 

[MachIVshooter]

Really? I knew the Desert Eagle was gas operated, but I didn't know what kind of action it used.

It's an AR style bolt and barrel extension, and a gas tube integral with the barrel that runs from just forward of the chamber to near the end of the tube (6" barreled gun). But in the case of the pistol, the gas piston is attached to the front of the slide, effectively making the slide an op rod.

The original 5.56 rifles were that light? I knew they were under seven pounds, and that's already excellent for a full length rifle, but five and a half is just ridiculous.

Almost makes me want to build one.

Yes, and sub-5 lb builds are pretty easy to do today, even with floating hand guards and adjustable stocks.

This is mine, weighs 4.87 lbs unloaded, including BUIS and the Trijicon red dot:



This one is just 6.77 lbs unloaded:



And yes, I'm well aware the flip up sights are backwards. I scarcely use them, and prefer the look.

 

[MechAg94]

[1] With around 4 million AR-15 and AR-15 style rifles in the US alone, it sure didn't do a good job for keeping it out of the civilian market...
[2] Actually, the cost of an M16, bought in Army volumes, is comparable to other military select-fire 5.56mm weapons, neither lower nor higher.
[3] But, 95 countries seem to find the M16 worth it.

Part of the explanation for the last one is that US foreign aide often has strings attached to spend the money on US made goods. US rifles are easy ways to spend that money.

In this day and time, AR parts and furniture is cheap compared to a lot of alternatives so if you want to put a collapsible stock on a new gun, AR furniture is a cheap and easy way to go. In addition, common magazines can make a new rifle more attractive.

 

[barnbwt]

"Part of the explanation for the last one is that US foreign aide often has strings attached to spend the money on US made goods. US rifles are easy ways to spend that money."
We also flat-out give away a metric buttload of the rifles, usually to some up-and-coming rebel group that will grow to bite us in the rear within five years' time, instead of surplussing them to American citizens. Mexico alone gets several train cars full of guns regularly as "drug war aid," which then filter to whatever nations/cartels they feel favorable towards, in South America as well as the Middle East.

Same reason the AK47 has such a following, despite having just about as many drawbacks as the AR. The VZ is about to get a lot more popular globally, also, as the Czechs just donated the rest of their surplus arsenal to fighters opposing Daesh, supposedly.

"Says you and a bunch of AK nuts[the DI system being a trouble spot]. The system works, and works well, whilst saving roughly 1/2 pound.

The reasons it is not copied have been pretty well laid out above, and have nothing to do with perceived shortcomings."
Well, we hear all the time from various folks that the reason X isn't, is because the market has decided there is no additional value in X over the existing Y (debatable, but whatever). Well...

-The AR15 platform has become somewhat ossified as a design due to its reliance on ultimate compatibility (locks down a ton of variables that would otherwise be open for modification), but this doesn't matter since it has become so compelling from an economic perspective. No cheaper rifle of this role has ever existed, and it is good enough as-is that there is basically no market demand to improve upon it more than incrementally (i.e. stagnation/commoditization)
-The AR15 platform design details are heavily utilized as inspiration for practically all cutting edge/clean sheet designs; this strongly implies that these traits are intrinsically valuable for a quality weapon. The AR15 gas system is quite simply not among those chosen by designers to emulate when given design freedom. Almost every clean sheet design from the last two decades uses a short stroke piston/guide rod system cribbed directly off the AR18, or less often a long-stroke system with very similar guide rod/rail scheme

The fact is, there is no reason any type of non-AR clone cannot copy the gas tube/bolt expansion chamber concept without turning into an AR clone itself. And yet nothing but AR clones use the gas tube to expansion chamber in the bolt gas system (except the Ares SCR as mentioned, which is trying its darndest to be an AR clone while accommodating ban state laws which have no bearing on gas system design). Rather, an awful lot of otherwise AR clones are bringing AR18 gas systems into the mix; the new HK service rifle and SIG MCX being the obvious examples. Rifles almost indistinguishable from ARs in practice...except for the gas system.

Why? They operate as well as any AR, but do so cleaner, and with greater comfort for the shooter (gas in face), while only adding a small measure of mass in an already absurdly light weight class. Substantial if unnecessary benefit, for hardly any weight cost (if only that were the only additional cost in going short stroke; all these guns are quite expensive compared to the pre-made AR platform)

TCB

 

[MistWolf]

I know that a piston only adds one part and a few ounces to a gun, on the other hand designs like the MAS or AR save you that piston

The AR has a piston. Its bolt is a piston. Its carrier is cylinder. The action of the AR will not function without its piston

 

[justin22885]

The lug designs are similar. The bolt itself, not so much. Unless you're trying to take it as far as calling all rotating bolts copies, in which case you gotta go back to the 19th century for origins.

I'll give you the barrel extension, had forgotten that about the Johnson, although there are still noteworthy differences.



Says you and a bunch of AK nuts. The system works, and works well, whilst saving roughly 1/2 pound.

The reasons it is not copied have been pretty well laid out above, and have nothing to do with perceived shortcomings.



Methinks you forget how light the original guns were; just 5-1/2 lbs with 20" barrels. Don't use the modern HBAR versions laden with accessories as a metric. You could, however, consider how far it's gone with modern carbines, title I guns weighing in at well under 5 lbs, some close to 3. I built a 4.6 lb title I AR for under $500. Find me a non-NFA Kalashnikopy that light. Heck, find me an AK SBR that's in the 4 lb range. Good luck.



Do not create false dichotomies of adulation and loathing.

so only me and a bunch of AK nuts say the AR gas system is the least desirable feature?.. then explain to me why no ones copied it since if its so fantastic?... so says me and just about every gun manufacturer on the planet

 

[USAF_Vet]

so only me and a bunch of AK nuts say the AR gas system is the least desirable feature?.. then explain to me why no ones copied it since if its so fantastic?... so says me and just about every gun manufacturer on the planet

This question has only been answered a few times in the thread. But here it is again.

It makes very little sense to copy the AR gas system and adapt it to another rifle. The AR gas system design works great, which is why there are so many AR copies and clones on the market. It's the same reason everyone and their sister makes a 1911, or a polymer frame striker fired handgun. The design works so well as originally intended that the only real modifications needed to copy it are scaling it up or scaling it down, relative to caliber.

Just about every other gun manufacturer on the planet produces a direct copy of the AR, sell them by the thousands, and make a ton of money.

But yeah, totally undesirable.

 

[justin22885]

if you knew how much it cost to pay engineers to design a weapon, to manufacture prototypes, extensive testing and trials to ensure the design is valid and safe, and then how difficult it is to get widespread demand for a new product that is unproven with no military usage, youd have to be able to pay millions in advertisement and marketing as well as need a factory large enough to mass produce them in high enough quantities to bring the price of the product down low enough to compete

ARs and 1911s arent the most duplicated because theyre the best, theyre duplicated because blueprints are widely available, patents are expired on both of them, both have long military history so they advertise themselves, no engineers need to be paid for coming up with a new design, and a lot of the components can easily be outsources to large factories already making parts (which is why most your AR "manufacturers" get completed or almost completed receivers from one of about 3 different factories

duplicating the AR-15 doesnt count as using the gas system design on a new rifle because these people arent making new rifles, theyre just producing copies of the same one.. not a single gun engineer since stoner worked on the AR-15 has sat down at his drafting table or launched a CAD program and implemented the AR15 gas system into another rifle.. there are cheaper, more reliable, less problematic systems out there...

the aug, tavor, sig 550, SCAR, ACR, XCR, CZ805, G36, beretta ARX 70/90, ARX 160, FNC, SA80, FAMAS, daewoo, QBZ 97, pindad, AK5, howa 89, FX-05 xiuhcoatl, radon FB MSBS, SAR-21, SAR-80, MKEK MPT-76, and F2000, and dozens of civilian rifles have been designed since, not a single one uses the AR15 gas system.. but if its the bestest most awesomest most reliable gas system in the whole wild world i wonder why its so neglected?

 

[meanmrmustard]

While I can't disagree with there being better pistols than 1911s, I can about ARs.

I'm a huge AK fan, but I recognize its limitations. One that comes to mind is changing to an appropriate caliber for the situation at hand. Not something that is difficult with the AR platform. So, why reinvent the wheel? It dont see it as lucrative to even try, and I can't count on ANY fingers the amount of folk clamoring for a DI rifle that isn't an AR.

How simple are the rifles, non DI as stated, to change? That being said, I can't see myself wishing I had one of them instead of an AR.

 

[justin22885]

AKs, ARs, FALs, HKs, M1As, SKS, take your pick, they all have things that are good and features that suck.. if either one was perfect there would never be an AR or AK debate, which is why i find such arguments so ridiculous as its two sides arguing the tradeoffs of different areas of imperfection

the problems with DI from a mathematical/engineering sense is the distance the gas must travel before it begins to move the bolt, the way gas works to move the bolt is the entire gas tube has to be pressurized with gas from the barrel in order to push it so because this expansion chamber is long, it must be very skinny or you may not get adequate pressure quick enough.. problem with DI systems like the MAS is the amount of force applied to the carrier is equal to the pressure in PSI multiplied by the surface area of the buttom of the "cup" in the face of the carrier, which is very small meaning little force

AR-15 remedies this by creating the expansion chamber inside the carrier for more surface area for the gasses to impinge against.. its not a bad design for what it was intended to do, but its not without its tradeoffs (added complexity, more parts, hot gas and fouling blown directly into the inner workings of your bolt).. generally speaking a piston is going to be more reliable, easier to tune, and not suffer the tradeoffs of DI

 

[meanmrmustard]

I dont know, man. Regardless of where gas and fouling go, there's cleaning to be done. My AKs piston cups and gas tubes can attest to that.

 

[MistWolf]

not a single gun engineer since stoner worked on the AR-15 has sat down at his drafting table or launched a CAD program and implemented the AR15 gas system into another rifle.. there are cheaper, more reliable, less problematic systems out there...

the aug, tavor, sig 550, SCAR, ACR, XCR, CZ805, G36, beretta ARX 70/90, ARX 160, FNC, SA80, FAMAS, daewoo, QBZ 97, pindad, AK5, howa 89, FX-05 xiuhcoatl, radon FB MSBS, SAR-21, SAR-80, MKEK MPT-76, and F2000, and dozens of civilian rifles have been designed since, not a single one uses the AR15 gas system.. but if its the bestest most awesomest most reliable gas system in the whole wild world i wonder why its so neglected?

AR-15...its not a bad design for what it was intended to do, but its not without its tradeoffs (added complexity, more parts, hot gas and fouling blown directly into the inner workings of your bolt).. generally speaking a piston is going to be more reliable, easier to tune, and not suffer the tradeoffs of DI

All reasons why the AR was immediately replaced by the US military and remains a little known and obscure rifle to this day

 

[MachIVshooter]

the problems with DI from a mathematical/engineering sense is the distance the gas must travel before it begins to move the bolt, the way gas works to move the bolt is the entire gas tube has to be pressurized with gas from the barrel in order to push it so because this expansion chamber is long, it must be very skinny or you may not get adequate pressure quick enough.. problem with DI systems like the MAS is the amount of force applied to the carrier is equal to the pressure in PSI multiplied by the surface area of the buttom of the "cup" in the face of the carrier, which is very small meaning little force

You make it quite clear that you lack the physics knowledge to make that assessment. Eugene Stoner did not, which is why the AR (again, not DI) works. Once you get it through your head that there are people who know more about this subject than you, and once you understand how the Stoner gas system actually works (hint: you won't call it DI anymore when you fully grasp it), then maybe we can get somewhere. Until then, it's just twaddle from someone who aspires to design firearms, but is hindered by his own hubris.

 

[WardenWolf]

Honestly, I think the main issue there is the reputation. The early M16's and AR's had a well-deserved reputation for poor reliability. As a result, other firearms designers wound up inventing their own systems to get around it. As time went on, people wound up basing new guns on these alternative actions rather than the AR action, simply because of that.

 

[Justin]

The number of rifle designs that do, or do not, use a particular operating system (independent of number of rifles fielded/applications for which the rifle is used/history or length of time the rifle has been in use/etc.) is a deeply weird metric to hang your hat on.

 

[Quentin]

Honestly, I think the main issue there is the reputation. The early M16's and AR's had a well-deserved reputation for poor reliability. As a result, other firearms designers wound up inventing their own systems to get around it. As time went on, people wound up basing new guns on these alternative actions rather than the AR action, simply because of that.

All reasons why the AR was immediately replaced by the US military and remains a little known and obscure rifle to this day

WardenWolf, the excellent MistWolf quote applies to your comment!

 

[justin22885]

You make it quite clear that you lack the physics knowledge to make that assessment. Eugene Stoner did not, which is why the AR (again, not DI) works. Once you get it through your head that there are people who know more about this subject than you, and once you understand how the Stoner gas system actually works (hint: you won't call it DI anymore when you fully grasp it), then maybe we can get somewhere. Until then, it's just twaddle from someone who aspires to design firearms, but is hindered by his own hubris.

says the one who thought stoner invented the multi-lug bolt and matching barrel extension or forgot that i already mentioned it wasnt a true DI all the way back on page 1

 

[MachIVshooter]

says the one who thought stoner invented the multi-lug bolt and matching barrel extension

Work on your reading comprehension. I said bolt design; the similar (not identical) lug pattern is the only thing they have in common. No separate bolt & carrier in the Johnson, totally different camming mechanism, different extractor, different ejector, etc. Saying that the lug design makes it a facsimile means you just as well call anything with two opposing lugs an 1886 Lebel ripoff.

Already gave you that I erred on the barrel extension, noting that they are also similar but not identical. I know to admit when I've made a mistake. You need to learn to do that.

forgot that i already mentioned it wasnt a true DI all the way back on page 1

Forget "not a true DI system"; it's not a DI system at all. It's a piston system without an op rod.

 

[benEzra]

I guess more generally, I don't know why DI never caught on.

It did catch on. "DI" rifles are manufactured by 40+ manufacturers in the U.S. alone, in calibers from .17 Remington to .50 Beowulf, and are the most popular civilian centerfire rifles in the United States.

As others have pointed out, the fact that most manufacturers have elected not to switch to proprietary Their-Company-Only parts is simply a recognition that the Stoner design has already had the bugs worked out of it, so their clean-sheet redesign would likely be less reliable out of the gate; economies of scale; and the fact that the broad parts interchangeability across different manufacturers and calibers is one of the platform's selling points (many buyers would avoid a proprietary system even if it offered a marginal improvement in some way over the AR). The AR has become a very refined system.

 

[justin22885]

and dont forget a proprietary system couldnt compete, to afford the engineers, the tooling of a factory, testing, this would all dictate an MSRP well above that of the AR-15 and without either military usage or a big brand name to back it, generating interest for something new would be very difficult at those prices

 

[USAF_Vet]

and dont forget a proprietary system couldnt compete, to afford the engineers, the tooling of a factory, testing, this would all dictate an MSRP well above that of the AR-15 and without either military usage or a big brand name to back it, generating interest for something new would be very difficult at those prices

Kel Tec.

 

[d2wing]

If you copy the DI you are going to end up with something much like an AR anyway. the only place for the piston is on top of the bolt. Otherwise you need action arms from the piston like a 7400 or M-14, or a combo piston operating rod like on the AK. To date the AR and AR-10 types cover so many bases that most of what we see are copies. Not only of the gas system but the entire rifle. By the same token we are seeing more copies of the AK design. the big sellers are civilian copies and variations on the same two designs.

 

[justin22885]

you see far, far more adaptations than the AR-18 (based on stoners AR-16) than anything else, no one else has put the AR gas system into a new rifle, a few but not that many have been adopting the AK gas system, but many, many rifles use a carrier and short-stroke system similar to the AR-18

 

[Billy Shears]

you see far, far more adaptations than the AR-18 (based on stoners AR-16) than anything else, no one else has put the AR gas system into a new rifle, a few but not that many have been adopting the AK gas system, but many, many rifles use a carrier and short-stroke system similar to the AR-18

I used to have a really nice Costa Mesa AR-180 that I regret having let get away. I've always thought that it was a better basic design for a general issue infantry rifle than the AR-15. It has almost all the AR-15's virtues (e.g. light weight, superior ergonomics, modularity [potential in this case, as the weapon was never developed like the AR-15 was, but there's no reason it couldn't have been]), and eliminates its one (arguable) vice -- the way the quasi-DI system of the AR-15 pumps hot gas and carbon fouling into the receiver. True, the AR-18 probably doesn't have as much potential for gilt-edged accuracy as the AR-15, but for a general issue infantry rifle, that really makes no difference whatsoever; the AR-18 had accuracy to spare for that role. All the flaws the AR-18 had -- it's rather flimsy folding stock, the less robust (stamped) fire control parts -- could have, and would have easily been worked out had the rifle undergone the kind of product improvement in service that the AR-15 did.